This invention relates to a semiconductor device, and more particularly a semiconductor device wherein a conductive film mainly composed of refractory metal such as W, Mo, Ti or Ta is employed as an electrode and/or an interconnection.
As already known, in MOS transistors of the prior art, a polycrystalline silicon film is most widely employed as a gate electrode and an interconnection which is formed solidly with the gate electrode and extends to the other region such as a drain of another MOS transistor.
However, along with remarkable improvement of an integration of a semiconductor device, it is proposed to employ a film of refractory metal such as W, Mo, Ti or Ta as a gate electrode and an interconnection.
Because such refractory metal has not only a high melting point but also much lower electrical resistance than polycrystalline silicon, it is not only resistant against high temperature thermal treatment but also very much suited for electrodes and interconnections between transistors with extremely fine dimensions.
However, there is a problem that when a source and a drain of an MOS transistor are formed by ionimplantation utilizing a gate electrode of such refractory metal film as a mask, ions penetrate through the gate electrode and are trapped in a channel region between a source and a drain.
There is also a problem that because of poor adhesiveness of the refractory metal film with an insulator film such as an SiO.sub.2 film, the electrode and the interconnection of refractory metal are easily peeled off from the insulator film substrate so that reliability of the semiconductor device is adversely affected.
Especially when a refractory metal film is formed on an SiO.sub.2 film by CVD (chemical vapor deposition), adhesion between the metal film and the SiO.sub.2 film is very weak so that improvement is obviously required.